Thanks for using our Answers Forum. I understand that your having trouble setting up your Slingbox for internet viewing. I do have a couple of questions for you, are you using your MAC wirelessly? If you are, I would recommend hard wiring it to your router just to guarantee that you are on the same network as your Slingbox.
Second, what browser are you using for your setup, I would recommend using Firefox, it seems to be the browser that works the best in the setup.
I do have an articles that will provide additional helpful information:
The last article explains how to get in contact with Support if you need further assistance.
Hope this helps.
Sling Moderation Team